1. Field of the Invention
The present invention relates generally to road construction. The present invention is more particularly a composition for prolonging the useful life of a road surface by sealing and strengthening the joints created during the paving process.
2. Description of the Prior Art
Highway paving is a huge industry. There are over 2.5 million miles of paved roads in the United States alone. Depending on the weather and level of usage the road surface may have to be repaired or replaced every 3-5 years. This represents a huge financial burden on the entity responsible for road maintenance.
One of the chief factors leading to premature road surface breakdown is cracking and disintegration around the joints between the sections (lanes) of asphalt pavement. There are two main causes leading to the formation of cracks in the joints between the lanes of asphalt pavement. The first area of premature deterioration causation is the temperature effect. First, the asphalt pavement shrinks as the ambient temperature drops during a seasonal temperature change. Asphalt pavements are strong when subjected to compressive loads; however, asphalt pavements do not have nearly as much resistance when subjected to tension (pulling apart) forces. The tension created by shrinkage, which occurs when the temperature decreases, is therefore very damaging to an asphalt surface, particularly around the joints. Second, the asphalt binder or glue used in the pavement deteriorates when subjected to heat. The manufacturing process used to make asphalt paving mixture by necessity subjects the asphalt binder material to high heat. Summer temperatures also heat the asphalt and contribute to the deterioration of the asphalt binder material, thereby reducing the resistance of the asphalt to stress, particularly to tension forces. The effects of the reduced resistance of the asphalt to cracking are most prevalent at the joint areas, where the asphalt pavement matrix is weakest.
The second chief cause of premature deterioration is the lack of compaction at the edges of a given asphalt pavement section. The area at and adjacent to the longitudinal joint of two asphalt highway lanes is difficult to compact during initial construction. The area to either side of the longitudinal joint (roughly plus or minus one foot from the joint) has less density or compaction than the balance of the pavement. The problem then is water and air intrusion into the area that is not as highly compacted. Water strips the asphalt coating from the asphalt pavement aggregate, thereby weakening the bond between coated aggregate pieces. In addition water absorbed in the critical non-compacted area freezes in winter conditions, causing mechanical damage to the area. Air entry into the pavement structure accelerates oxidation of the asphalt binder reducing its glue-like properties.
There is a need for a composition that will seal joints in asphalt surfaces, thereby prolonging the useful life of the surface.